DE69829936T2 - Ceramic cutting tool - Google Patents

Description

The The present invention relates to a ceramic cutting tool. In particular, the present invention relates to a ceramic Cutting tool suitable for cutting e.g. spherulitic cast iron (nodular cast iron) suitable is.

In The past few years have shown in terms of increasing the Speed and efficiency of machining become faster Progress. High performance ceramic materials with this tendency Can keep up, were in demand. For example, titanium carbonitride has a high Melting point and hardness and a low thermal expansion coefficient and shows no drop in thermal conductivity at high temperatures. Therefore, titanium carbide is a high temperature high temperature material Thermal shock resistance known. Titanium carbide, however, can hardly be sintered. It was therefore, as essential considers that titanium carbide is complexed with a metal is such as Co and Ni to form a cermet, the allows, to obtain a dense sintered product suitable for cutting tools etc. can be used. Cermet, however, has some disadvantages on. Because the integrated metals degrade the heat resistance of cermet, let yourself Hard to say that the excellent heat resistance of titanium carbide is effective can be brought to bear. For example, if a cutting tool from Cermet for the high-speed processing of a material based on Iron having high strength and ductility, such as nodular Cast iron, used, it achieves due to its weak heat resistance soon the end of his life.

Around to eliminate these difficulties became a ceramic material proposed on a titanium carbide basis, which is a solid solution of a Metal in titanium carbide has adverse effects on high temperatures to counteract and improved heat resistance (JP-B-2-25866 (the term "JP-B" as used herein means an "examined Japanese Patent Publication "), JP-A-62-36065 (incorporated herein) used term "JP-A" means an "unaudited Japanese Patent publication)). Although the ceramic disclosed in the above publications Material a good heat resistance it disadvantageously has a much lower strength than the previous cermet and tends to fragmentation.

on the other hand was conceived as a titanium carbide based ceramic material containing a has improved strength and at the same time its good high-temperature properties maintains, one proposed, then integrated silicon carbide whisker crystals contains (JP-B-8-16028). Although this ceramic material is based on titanium carbide due to the incorporation of silicon carbide whisker crystals having improved strength, it disadvantageously tends to that silicone in the whiskers with iron in the to be cut Material reacts, causing a remarkable deterioration the abrasion resistance leads, when it comes to cutting a material based on iron, in particular nodular Cast iron, is used.

A The object of the present invention is a ceramic cutting tool to provide that mainly a hard phase based on titanium with excellent heat resistance and abrasion resistance, which has excellent strength and is capable of a solid material based on Iron, such as spherulitic Cast iron, to cut.

The ceramic cutting tool defined in a first aspect of the present invention comprises in its essential part a ceramic material mainly comprising a titanium carbonitride-based hard phase mainly comprising titanium carbonitride and having an alumina-based phase mainly aluminum oxide, wherein the titanium carbonitride-based hard phase and the alumina-based phase satisfy the following relationships: 10 wt% ≤ WAl ₂ O ₃ ≤ 45 wt%; 51% by weight ≦ WTiCN ≦ 89.5% by weight; and 96% by weight ≦ WAl ₂ O ₃ + WTiCN ≦ 99.5% by weight, wherein WAl ₂ O ₃ indicates the proportion by weight of aluminum, calculated in the form of Al ₂ O ₃ ; and WTiCN indicates the weight ratio of the hard phase of the titanium carbonitride with the condition that WTiCN is defined by WTi + WC + WN, where WTi, WC and WN are each the weight ratio of the titanium component, the carbon component and the nitrogen component.

The The invention will now be described with reference to exemplary embodiments and the following accompanying drawings:

1A - 1C Fig. 3 are a perspective view, a schematic side view in partial section and a partially enlarged view of the ceramic cutting tool test piece used in the examples, respectively;

2A - 3D are schematic representations illustrating the scope of the cutting test; and

3A - 3C Figures 10 are top, left side and front views illustrating the position of the ceramic cutting tool test piece with respect to work in the cutting test.

In the ceramic material used for the cutting tool is used as in the first aspect of the present invention comprises titanium carbonitride, mainly the hard phase, the benefits of titanium carbide, the one excellent heat resistance and has high strength, and of titanium nitride, which has a has excellent strength. In this way, a ceramic Cutting tool with excellent heat resistance and abrasion resistance accomplished become. Furthermore, alumina, which is mainly the Phase based on alumina forms, a chemical stable Substance with excellent acid resistance, which generates a small amount of free energy. The dispersion of alumina in titanium carbon nitride it, the acid resistance and chemical stability of the ceramic material as a whole. Even if it is therefore used for cutting iron-based material is, the ceramic material is not subject to excessive reaction, causing it possible will further improve the abrasion resistance of the cutting tool. Allowing these effects altogether it, a solid iron-based material, such as Sphärolithi sches Cast iron, cut at a high speed and a perform ceramic cutting tool with a longer life.

WAl ₂ O ₃ corresponding to the alumina content in the ceramic material is set in a range of 10 to 45 wt%. WTiCN corresponding to the content of titanium carbonitride-based hard phase in the ceramic material is adjusted to a range of 51 to 89.5 wt%. Furthermore, WAl ₂ O ₃ , + WTiCN are adjusted to a range of 96 to 99.5 wt%. These values have the following crucial meanings.

When WAl ₂ O ₃ falls below 10% by weight, the resulting effect on improving the acid resistance and chemical stability of the ceramic material is insufficient. In contrast, when WAl ₂ O ₃ exceeds 45% by weight, the relative content of titanium carbonitride (ie, WTiCN) is reduced, whereby the ceramic material becomes less heat-resistant and hard. It is preferred that WAl ₂ O ₃ be adjusted to a range of 20 to 30 wt%, thereby taking into account the balance between hardness and strength of the ceramic material.

If WTiCN falls below 51% by weight, the relative content of titanium carbonitride (i.e., WTiCN) is reduced, whereby the ceramic material is less heat resistant and hard. If WTiCN in contrast exceeds 89.5 wt .-%, the relative content of alumina is reduced, causing the Effect on improving the acid resistance and chemical stability of the ceramic Material becomes insufficient. It is preferred that WTiCN be applied to one Range is set from 66 to 79.5 wt .-%.

Further, when WAl ₂ O ₃ + WTiCN falls below 96% by weight, the content of the aluminum oxide and titanium carbonitride which mainly forms the ceramic material is insufficient, making it impossible to obtain the desired tooling properties. On the other hand, when WAl ₂ O ₃ , + WTiCN exceeds 99.5 wt%, the content of a sintering aid component, which will be described later, is insufficient, making it impossible to obtain a high-density sintered product.

The in a second aspect of the present invention Ceramic cutting tool is a ceramic cutting tool according to the first Aspect of the present invention, wherein KN / (KC + KN) and KTi / (KC + KN) to a range of more than 0 to not more than 0.5 and not less than 0.6 to not more than 0.9 are assuming that KTi is the molar content of the Ti component in the ceramic material, KC is the molar content of the C component in the ceramic material, and KN is the molar content of the N component in the ceramic material.

As previously mentioned, Titanium carbonitrile has both the advantages of titanium carbide, the an excellent heat resistance and a high hardness owns, as well as titanium nitride, which is an excellent Has strength. The setting of the value of KN / (KC + KN) allows a good balance of the former properties and the latter properties. For example, if desired, in particular hardness or heat resistance to increase, For example, the value of KN / (KC + KN) can be slightly reduced, i. of the Content of the C component can be increased become. On the contrary, if it is desired to ensure a higher strength, the value of KN / (KC + KN) can be previously set slightly higher, i. the content of the N component can be increased. If the value of KN / (KC + KN) exceeds 0,5, the resulting ceramic material may be insufficient Hardness or heat resistance exhibit. The value of KN / (KC + KN) is preferably no longer than 0.3.

If the value of KTi / (KC + KN), which is the ratio of the content of the Ti component to that of the content of light elements (C, N) is below 0.6 drops, can settle unstable compounds that may cause the chemical stability of the ceramic material or affect the high temperature properties of the material. On the other hand, if the value of KTi / (KC + KN) exceeds 0.9, can settle free light elements, or the sinterability The material may deteriorate, easily forming voids can, which the hardness, Reduce the strength or strength of the material.

The in a third aspect of the present invention Ceramic cutting tool is a ceramic cutting tool according to the first or zwei th aspect of the present invention, wherein the titanium carbonitride-based hard phase average particle diameter in the ceramic material is not more than 0.5 microns.

The previous definition of the average particle diameter the titanium carbonitride based hard phase on the above defined Area allows it is to carry out a ceramic cutting tool, which further comprises a excellent hardness, Has resistance and strength. The average Titanium carbonitride-based hard phase particle diameter is preferably previously set to not more than 0.3 μm. The average Particle diameter of the alumina phase is preferably not previously more than 1.0 μm set to a ceramic material with sufficient resistance and hardness provide.

The ceramic cutting tool defined in a fourth aspect of the present invention is a ceramic cutting tool according to any one of the first to third aspects of the present invention, wherein the ceramic material comprises a sintering aid component mainly containing metal oxides other than Al ₂ O ₃ with an integrated therein Proportion of 0.5 to 4 wt .-%.

The Integration of such a sintering aid component in the ceramic Material allows the acceleration of the sintering process, which allows is, constantly a dense ceramic cutting tool with a to obtain high resistance. If the content of the sintering aid component below 0.5% by weight, can the aforementioned effects are not sufficiently effective to be brought. In contrast, if the content of the sintering aid component Exceeds 4% by weight, can the heat resistance of the material become.

The ceramic cutting tool defined in a fifth aspect of the present invention is a ceramic cutting tool according to any one of the first to fourth aspects of the present invention, wherein the ceramic material has one or more metallic components selected from the group consisting of Mg, Ca, Zr , Hf and R (wherein R comprises one or more rare earth elements selected from the group consisting of Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm , Yb and Lu), which are then incorporated with a total amount of from 0.5 to 4% by weight, which is in the form of MgO for Mg, CaO for Ca, ZrO ₂ for Zr, HfO ₂ for Hf, CeO ₂ for Ce, Pr ₆ O ₁₁ for Pr, Tb ₄ O ₇ for Tb and M ₂ O ₃ for the rest of the metallic components was calculated (where M represents the rare earth elements excluding Ce, Pr and Tb).

The aforementioned metal components can be integrated into the material in the form of oxide. During sintering, these metal components are melted and sintered to form a liquid phase which acts as a sintering aid to accelerate the sintering process. It is believed that these metal components in the thus-sintered metal are mostly in the form of oxide. However, these metal components often form an amorphous glass phase and thus can hardly be identified in the form of single oxide. In this case, the total content of these metal components range from 0.5 to 4 wt .-%, as calculated in the form of single oxide. When the content of these metal components as calculated in the form of oxide falls below 0.5% by weight, a dense ceramic material can hardly be obtained. In contrast, when the content of these metal components as calculated in the form of oxide exceeds 4% by weight, the heat resistance of the material may be impaired.

The ceramic cutting tool defined in a sixth aspect of the present invention is a ceramic cutting tool according to any one of the first to fifth aspects of the present invention, wherein the ceramic material has a breaking strength of not less than 5.6 MPam ^½ .

The in an eighth aspect of the present invention Ceramic cutting tool is a ceramic cutting tool according to any the first to sixth aspects of the present invention, wherein the ceramic material has a Vickers hardness Hv of not less than 2,200.

The Application of the present invention makes it possible to use a ceramic Execute cutting tool, which has a high strength and a high hardness, as previously mentioned. The In this way, obtained ceramic cutting tool can be a solid Iron-based material, such as spherulitic Cast iron, cut easily at a high speed. The breaking strength value as used in here gives the Value obtained by the IF method (indentation-fracture method) from the breaking strength test method measured in JIS-R1607 (1990).

Of the Process for producing the aforementioned cutting tool (ceramic Material) is described below.

The Mixing and milling of the starting material powder can by means of a known mixing agent, such as ball mill, stirred ball mill and V-blender. In titanium carbonitride the value of KN / (KC + KN) or KTi / (KC + KN) must be set become. The adjustment of these values can be done by adjusting the mixing ratio Titanium carbide powder and titanium nitride powder, which as Starting materials are used. Alternatively, titanium carbonitride with a desired one mixing ratio be used by carbon and nitrogen. Alternatively, you can a treatment such as nitriding and decarburization in one non-oxidizing atmosphere as a sintering atmosphere to adjust the value of KN / (KC + KN) or KTi / (KC + KN).

The The aforementioned raw material powder can be in a desired shape be formed and then be subjected to sintering, such as hot pressing, normal sintering and HIP treatment to produce a cutting tool. While sintering, the starting material must be heated to a temperature of 1,500 ° C to 2,000 ° C.

EXAMPLES

The The present invention will be further described in the following examples.

• (1) TiC_0,9 und Ti(C_0,7N_0,3)_0,85 mit einem durchschnittlichen Teilchendurchmesser von 1,0 μm;
• (2) Al₂O₃ mit einem durchschnittlichen Teilchendurchmesser von 0,8 μm; und
• (3) CaO, MgO, ZrO₂, Y₂O₃, Yb₂O₃ und Dy₂O₃ mit einem durchschnittlichen Teilchendurchmesser von 0,8 bis 2 μm.

As starting materials, the following materials were used:

• (1) TiC _0.9 and Ti (C _0.7 N _0.3 ) _0.85 having an average particle diameter of 1.0 μm;
• (2) Al ₂ O ₃ having an average particle diameter of 0.8 μm; and
• (3) CaO, MgO, ZrO ₂ , Y ₂ O ₃ , Yb ₂ O ₃ and Dy ₂ O ₃ having an average particle diameter of 0.8 to 2 μm.

The different starting materials were used in a pre-determined relationship and then wet-ground with acetone for 30 hours in a stainless steel ball mill. Thereafter, the mixture was dried in a dryer to acetone to evaporate. In this way, a base powder was obtained.

• (1) Heißpressen bei einem Druck von 200 kgf/cm² in Ar-Atmosphäre für 30 Minuten (im Folgenden nur als "H.P." bezeichnet);
• (2) Normales Sintern unter reduziertem Druck in einer Atmosphäre von (Ar + N₂) für 1 Stunde (im Folgenden nur als "NS" bezeichnet); und
• (3) Primäres Sintern unter reduziertem Druck in einer Atmosphäre von (Ar + N₂) für 1 Stunde, gefolgt von sekundärem Sintern mit heißisostatischem Pressverfahren (HIP) bei 1.500 °C und 1.500 atm in AR-Atmosphäre für 2 Stunden (im Folgenden nur als "HIP" bezeichnet).

The base powder was sintered at the sintering temperature shown in Table 1 by the sintering method shown in Table 1 to obtain a cutting tool, which was then subjected to a comparative test with Comparative Examples. In the present example, the following sintering methods were used:

• (1) hot pressing at a pressure of 200 kgf / cm ² in Ar atmosphere for 30 minutes (hereinafter referred to as "HP"only);
• (2) Normal sintering under reduced pressure in an atmosphere of (Ar + N ₂ ) for 1 hour (hereinafter referred to as "NS"only); and
• (3) Primary sintering under reduced pressure in an atmosphere of (Ar + N ₂ ) for 1 hour, followed by secondary hot isostatic pressing (HIP) sintering at 1,500 ° C and 1,500 atm in AR atmosphere for 2 hours (hereinafter only referred to as "HIP").

In the methods (2) and (3), nitriding or decarburization was carried out simultaneously with sintering at different mixing ratios of Ar and N ₂ and atmospheric pressures to adjust the composition of the sintered product.

The sintered product thus obtained was polished with a diamond grinding wheel to prepare the cutting tool test piece with a shape to be inserted in the 1A - 1C is shown (defined in ISO as SNGN120408). In some detail was the test piece 1 a flat prism with an almost square average with a side length of about 12.7 mm and a thickness of about 4.76 mm. The corner 1a had a curvature radius R of about 0.8 mm. The edge section 1b was tapered so that the width t of the chamfer on the side of the main plane 1c was about 0.1 mm, and the inclination angle θ of the taper with respect to the principal plane 1c about 25 °.

The different test pieces were each polished to a high gloss and then to density ratio to theoretical Value (relative density), compressive strength and Vickers hardness measured. For the Measurement of breaking strength (Kc) became that defined in JIS-R1607 (1990) IF method used. In some detail a Vickers imprint stamp became (Vickers indenter) for 30 seconds under a load of 30 kgf pressed against the test piece. The Vickers hardness was determined by the imprint area and the load. The Test piece was on polished surface observed by a scanning electron microscope. From the picture thus obtained became the average particle diameter of the hard phase titanium carbonitride-based (or titanium carbide-based hard phase) determined. The results are shown in Table 2.

To determine the composition of the various test pieces, the weight fraction of the Ti component (WTi), Al component (WAl) and metal component was identified as a sintering aid by means of fluorescence X-ray analysis, and the weight fraction of the C component (WC) and the N component ( WN) was determined by gas analysis. Subsequently, WAl was converted to oxide base (converted to oxide base) to determine the weight fraction of alumina WAl ₂ O ₃ . The weight fraction of the hard phase (WTiCN) or WTiC) was determined from WTi + WC + WN (or WTi + WC). The various parts by weight were converted to molar contents to obtain the above value of KN / (KC + KN) and KTi / (KC + KN). The results are shown in Table 1. Auger electron spectroscopy and X-ray photoelectron spectroscopy showed that almost all of the C components and N components are integrated into the sintered product in the form of a composite with titanium, ie, the titanium carbonitride-based hard phase or the hard phase on titanium carbide. Be integrated.

The various test pieces (ceramic Cutting tool) were subjected to cutting properties under the following conditions rated.

(Cutting test for abrasion resistance)

A bar product (working material) W with an in 2A shown shape was rotated about its axis. In the 1A - 1C shown test piece 1 that was supported by a holder was allowed to come into contact with the outer circumference of the product W, as in 2C shown. With one of the main levels 1c as chip surface, (hereinafter referred to as " 1c "), and the side surface 1e ( 1A - 1C ) as a relief surface, the outer circumference of the product W was wet-blended continuously under the following conditions:
Product: spherulitic cast iron (JIS: FCD600), round rod (outer diameter ∅: 240 mm, length: 200 mm)
Cutting speed V: 250 m / min
Feed f: 0.2 mm / turn
Cutting depth d: 0.5 mm
Cutting oil: water-soluble cutting oil type W1, No. 1, Z (one defined in JISK2241 (1986) or one having not less than 90% of emulsified nonvolatile content of pH 8.5 to 10.5, and 0 to 30% by weight of an aliphatic acid, 50 to 80% by weight of a mineral oil and 15 to 35% by weight of a having surfactant).

The position of the test piece 1 with regard to product 1 is further included in 3A - 3C illustrated. In the 3A - 3C gives 1g the normal page-saving surface, and 1f indicates the front recess surface. Further, O denotes a center axis of the product W, D denotes a straight line passing through the horizontal center of the test piece and parallel to the diagonal line of the main plane 1c ' is (intersects with O), E denotes an intersection of D with the outer circumference of the product W (cutting point through the test piece), J denotes a straight line passing through E and intersecting with O, K a plane passing through the horizontal center of the test piece and parallel to the main plane 1c ' φ denotes a intersection angle of J with D, and δ indicates a helix angle of K with respect to θ.

Judgment: After completion of the cutting operation, the abrasion Vn on the recessed side of the cutting edge became (amount of abrasion in the cutting direction on the normal side recessed surface 1g : please refer 2D ).

(Cutting test for loss resistance) (loss resistance)

A bar product W with an in 2D shown shape was rotated about its axis. In the 1A - 1C shown test piece 1 was allowed to come into contact with the outer circumference of the product W, as in 2C shown. With one of the main levels 1c as chip surface, (hereinafter referred to as " 1c "), and the side surface 1e as the recess surface, the outer circumference of the product W was continuously wet-blasted under the following conditions:
Product: Spherolitic cast iron (JIS: FCD600), round rod with 12 longitudinal grooves provided at regular intervals (outer diameter ∅: 240 mm, length: 200 mm, groove depth: 40 mm, groove width: 5 mm)
Cutting speed V: 150 m / min
Feed f: 0.25 mm / turn
Cutting depth d: 0.5 mm
Cutting oil: the same as used for the abrasion resistance cutting test
Assessment: A number of exposures are required until a loss of entry (number of passes across the grooves)

The Results are given in Table 2.

These Results show that the ceramic cutting tool test pieces according to the present invention Invention have cutting properties, both for abrasion resistance and loss resistance outstanding are.

Claims (8)

A ceramic cutting tool having in its substantial part a ceramic material, the ceramic material having a titanium carbonitride-based hard phase comprising titanium carbonitride and an alumina-based phase comprising aluminum oxide, the ceramic material satisfying the following relationships: 10 wt% ≤ WAl ₂ O ₃ ≤ 45 wt%; 51% by weight ≦ WTiCN ≦ 89.5% by weight; and 96% by weight ≦ WAl ₂ O ₃ + WTiCN ≦ 99.5% by weight, wherein WAl ₂ O ₃ indicates the proportion by weight of aluminum, calculated in the form of Al ₂ O ₃ ; and wherein WTiCN indicates the weight content of the titanium carbonitrile hard phase, with the proviso that WTiCN is defined by WTi + WC + WN, where WTi, WC and WN are the proportion by weight of the titanium components, the carbon components and the nitrogen components, respectively, are. A ceramic cutting tool according to claim 1, wherein KN / (KC + KN) and KTi / (KC + KN) to a range greater than 0 to not more than 0.5 and not less than 0.6 to no more as 0.9, respectively, are set, assuming that KTi is the molar content of the Ti components in the ceramic material, KC is the molar content of the C components in the ceramic material and KN is the molar content of the N components in the ceramic Material is. A ceramic cutting tool according to claim 1 or 2, wherein the average particle diameter of titanium carbonitride no longer based hard phase in the ceramic material than 0.5 μm is. A ceramic cutting tool according to any one of claims 1 to 3, wherein the ceramic material comprises a sintering aid component mainly comprising metal oxides other than Al ₂ O ₃ used therein in an amount of 0.5 to 4% by weight. A ceramic cutting tool according to any one of claims 1 to 4, wherein the ceramic material comprises one or more metallic component (s) selected from the group consisting of Mg, Ca, Zr, Hf and R (wherein R has one or more rare earth elements, selected from the group consisting of Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu) used therein in a total amount of 0.5 to 4 wt .-%, calculated in the form of MgO for Mg, CaO for Ca, ZrO ₂ for Zr, HfO ₂ for Hf, CeO ₂ for Ce, Pr ₆ O ₁₁ for Pr, Tb ₄ O ₇ for Tb and M ₂ O ₃ for the rest of the metallic components (where M represents the rare earth elements, excluding Ce, Pr and Tb). A ceramic cutting tool according to any one of claims 1 to 5, wherein the ceramic material exhibits a breaking strength of not less than 5.6 MPam ^½ . Ceramic cutting tool according to one of claims 1 to 6, wherein the ceramic material has a Vickers hardness Hv of not less than 2,200 shows. A ceramic cutting tool according to any one of claims 1 to 7, wherein the ceramic material satisfies the following relationship: 66 wt% ≤ WTiCN ≤ 79.5 wt%.